The Marine Mammal Protection Act of 1972 (MMPA) was the first act of the United States Congress to call specifically for an ecosystem approach to natural resource management and conservation. It was signed into law on October 21, 1972 (and took effect 60 days later on December 21, 1972) by President Richard Nixon. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal, along with any marine mammal part or product within the United States. The Act defines "take" as "the act of hunting, killing, capture, and/or harassment of any marine mammal; or, the attempt at such." The MMPA defines harassment as "any act of pursuit, torment or annoyance which has the potential to either: a. injure a marine mammal in the wild, or b. disturb a marine mammal by causing disruption of behavioral patterns, which includes, but is not limited to, migration, breathing, nursing, breeding, feeding, or sheltering." The MMPA provides for enforcement of its prohibitions, and for the issuance of regulations to implement its legislative goals.

The MMPA prohibits the take and exploitation of any marine mammal without appropriate authorization, which may only be given by the Service. Permits may be issued for scientific research, public display, and the importation/exportation of marine mammal parts and products upon determination by the Service that the issuance is consistent with the MMPA’s regulations. The two types of permits issued by the National Marine Fisheries Service's Office of Protected Resources are incidental and directed. Incidental permits, which allow for some unintentional taking of small numbers of marine mammal, are granted to U.S. citizens who engage in a specified activity other than commercial fishing in a specified geographic area. Directed permits are required for any proposed marine mammal scientific research activity that involves taking marine mammals.

Applications for such permits are reviewed and issued the Service's Division of Management Authority, through the International Affairs office. This office also houses the Division of International Conservation, which is directly responsible for coordinating international activities for marine mammal species found in both U.S. and International waters, or are absent from U.S. waters. Marine mammal species inhabiting both U.S. and International waters include the West Indian manatee, sea otter, polar bear, and Pacific walrus. Species not present in U.S. waters include the West African and Amazonian manatee, dugong, Atlantic walrus, and marine otter.

In efforts to conserve and manage marine mammal species, the Service has appointed field staff dedicated to working with partners to conduct population censuses, assess population health, develop and implement conservation plans, promulgate regulations, and create cooperative relationships internationally.

Various Marine Mammal Management offices are located on either coast. The Service's Marine Mammal Management office in Anchorage, Alaska is responsible for the management and conservation of polar bears, Pacific walruses, and northern sea otters in Alaska. Northern sea otters present in Washington State are managed by the Western Washington Field Office, while southern sea otters residing in California are managed by the Ventura Field Office. West Indian manatee populations extend from Texas to Rhode Island, and are also present in the Caribbean Sea; however, this species is most prevalent near Florida (the Florida subspecies) and Puerto Rico (the Antillean subspecies). The Service’s Jacksonville Field Office manages the Florida manatee, while the Boqueron Field Office manages the Antillean manatee.

The polar bear, southern sea otter, marine otter, all three species of manatees, and the dugong are also concurrently listed under the Endangered Species Act (ESA).

Amendments enacted in 1981 established conditions for permits to be granted to take marine mammals "incidentally" in the course of commercial fishing. In addition, the amendments provided additional conditions and procedures for transferring management authority to the States, and authorized appropriations through FY 1984.

Policies created in 1982

Some marine mammal species or stocks may be in danger of extinction or depletion as a result of human activities.

These species or stocks must not be permitted to fall below their optimum sustainable population level (depleted)

Measures should be taken to replenish these species or stocks

There is inadequate knowledge of the ecology and population dynamics

Marine mammals have proven to be resources of great international significance.

The 1984 amendments established conditions to be satisfied as a basis for importing fish and fish products from nations engaged in harvesting yellowfin tuna with purse seines and other commercial fishing technology, as well as authorized appropriations for agency activities through FY 1988.

Amended in 1988

the establishment of conditions and procedures for the Secretaries of Commerce and Interior to review the status of populations to determine if they should be listed as "depleted" (below optimal, sustainable population numbers or listed as threatened or endangered);

the preparation of conservation plans for any species listed as depleted, including a requirement that such plans be modeled after recovery plans developed pursuant to the Endangered Species Act;

the listing of conditions under which permits may be issued to take marine mammals for the protection and welfare of the animals, including importation, public display, scientific research, and enhancing the survival or recovery of a species; and

a reward system under which the Secretary of the Treasury can pay up to $2500 to individuals providing information leading to convictions for violations of the Act.

Amended in 1995

Certain exceptions to the take prohibitions, such as for Alaska Native subsistence and permits and authorizations for scientific research;

A program to authorize and control the taking of marine mammals incidental to commercial fishing operations;

Preparation of stock assessments for all marine mammal stocks in waters under U.S. jurisdiction; and

Congress found that: all species and population stocks of marine mammals are, or may be, in danger of extinction or depletion due to human activities; these mammals should not be permitted to diminish below their optimum sustainable population; measures should be taken immediately to replenish any of these mammals that have diminished below that level, and efforts should be made to protect essential habitats; there is inadequate knowledge of the ecology and population dynamics of these mammals; negotiations should be undertaken immediately to encourage international arrangements for research and conservation of these mammals. Congress declared that marine mammals are resources of great international significance (aesthetic, recreational and economic), and should be protected and encouraged to develop to the greatest extent feasible commensurate with sound policies of resource management. The primary management objective should be to maintain the health and stability of the marine ecosystem. The goal is to obtain an optimum sustainable population within the carrying capacity of the habitat.